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Phase change material could have application in memories and batteries

MIT associate professor Bilge Yildiz. pic: Denis Paiste/Materials Processing Center

Researchers at MIT have developed a thin film material whose phase and electrical properties can be switched between metallic and semiconducting by applying a small voltage. The material then stays in its new configuration until switched back by another voltage. According to the researchers, their discovery could enable a new kind of non volatile memory.

Associate professor Bilge Yildiz said the structural phase of a strontium cobaltite (SrCoOx) is usually controlled by its composition, temperature, and pressure. “We have demonstrated that electrical bias can induce a phase transition in the material.”

Researcher Qiyang Lu added: “It has two different structures that depend on how many oxygen atoms per unit cell it contains and these two structures have quite different properties.”

When more oxygen is present, it forms a perovskite, whereas lower concentrations of oxygen produce a brownmillerite and both forms have different chemical, electrical, magnetic and physical properties. Lu and Yildiz found the material can be flipped between the two forms with the application of 30mV. And, once changed, the new configuration remains stable until it is flipped back by a second application of voltage.

In addition to memories, the material could also find application in fuel cells and electrodes for lithium ion batteries.

The team is now working to better understand the electronic properties of the material in its different structures and to extend this approach to other oxides of interest for memory and energy applications.

Graham Pitcher

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